Ok heres what your gonna have to do, take the side panel off your case (yes take the panel off the case
see if the board has any numbers letter or number groups like the picture bellow, right them down on a piece of paper, if there is any. Then look for the crystal that has the number similar to the 2nd picture bellow(it wont be the same but it has to start with 14.) once you find that crystal look for the chip right next to it(normaly it has ICS and a bunch of numbers on it like the picture bellow) you need to right them down as well. Now youve figured out which clockgen you have so now you can put the PC back together. Go to this link http://www.cpuid.com/clockgen.php
scroll down the page a little bit and see if your board or your clockgen chip is listed, if it is then download the one you need. If its not then try another progeam called CPUFSB, which can be found here http://www.majorgeeks.com/CPUFSB_d420.html
, you need to download this and install it.
Once again youll have to see if your board is listed, if not then youll have to find your clockgen number in the list (CPUFSB supports alot more chips)
Now when I first started doing this I did it all on my own with little help, so here I have pretty much did all the work for you, so what you do from here is up to you.